Help, big error, dd first GB of a raid:-/

Help, big error, dd first GB of a raid:-/

[Lars Schimmer]

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Hi!

Due to a very bad idea/error, I zeroed my first GB of /dev/md0.
Now fdisk doesn't find any disk on /dev/md0.
Any idea on how to recover?

MfG,
Lars Schimmer
- --
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TU Graz, Institut für ComputerGraphik & WissensVisualisierung
Tel: +43 316 873-5405       E-Mail: l.schimmer@cgv.tugraz.at
Fax: +43 316 873-5402       PGP-Key-ID: 0x4A9B1723
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Re: Help, big error, dd first GB of a raid:-/

[Peter Rabbitson]

Lars Schimmer wrote:
> 
> Hi!
> 
> Due to a very bad idea/error, I zeroed my first GB of /dev/md0.
> Now fdisk doesn't find any disk on /dev/md0.
> Any idea on how to recover?
> 

It largely depends on what is /dev/md0, and what was on /dev/md0. Provide very 
detailed info:

* Was the MD device partitioned?
* What filesystem(s) were residing on the array, what sizes, what order
* What was each filesystem used for (mounted as what)

Someone might be able to help at this point, however if you do not have a 
backup - you are in very very deep trouble already.

Re: Help, big error, dd first GB of a raid:-/

[Lars Schimmer]

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Peter Rabbitson wrote:
> Lars Schimmer wrote:
>>
>> Hi!
>>
>> Due to a very bad idea/error, I zeroed my first GB of /dev/md0.
>> Now fdisk doesn't find any disk on /dev/md0.
>> Any idea on how to recover?
>>
> 
> It largely depends on what is /dev/md0, and what was on /dev/md0.
> Provide very detailed info:
> 
> * Was the MD device partitioned?
> * What filesystem(s) were residing on the array, what sizes, what order
> * What was each filesystem used for (mounted as what)

One large parttiton on /dev/md0 with ext3.

> Someone might be able to help at this point, however if you do not have
> a backup - you are in very very deep trouble already.

I activate the backup right now - was OpenAFS with some RW volumes -
fairly easy to backup, but...
If it's hard to recover raid data, I recreate the raid and forget the
old data on it.

MfG,
Lars Schimmer
- --
- -------------------------------------------------------------
TU Graz, Institut für ComputerGraphik & WissensVisualisierung
Tel: +43 316 873-5405       E-Mail: l.schimmer@cgv.tugraz.at
Fax: +43 316 873-5402       PGP-Key-ID: 0x4A9B1723
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Re: Help, big error, dd first GB of a raid:-/

[Peter Rabbitson]

Lars Schimmer wrote:

> I activate the backup right now - was OpenAFS with some RW volumes -
> fairly easy to backup, but...
> If it's hard to recover raid data, I recreate the raid and forget the
> old data on it.

It is not that hard to recover the raid itself, however the ext3 on top is 
most likely FUBAR (especially after 1GB was overwritten). Since like it seems 
the data is not that important to you, just roll back to a backup and move on.